Types of Reservoirs in the Petroleum Industry

Naturally occurring hydrocarbon fluids are found in a reservoir. These fluids are a mixture of different organic compounds that exhibit varying behaviors over a broad range of temperatures and pressures. The variations in behavior and physical properties of the reservoir rock determine the ease at which liquids and gases are retained or transmitted.

Petroleum consulting is essential in determining the type of reservoir you have. There are different types of reservoirs in the petroleum sector, depending on their pressure rating on a pressure-temperature envelope.

Undersaturated Oil Reservoirs

The reservoir pressure in these reservoirs is at point one on the pressure-temperature envelope. The Pi is higher than the Pb. The Pi is the initial reservoir pressure while the Pb is the reservoir fluid’s bubble point pressure. This oil reservoir isn’t saturated with gas bubbles; hence, the pressure keeps all light gaseous hydrocarbons inside the crude oil.

The state of undersaturation in this reservoir also means that if there are any bubbles present in the reservoir, the oil will comfortably absorb them.

Saturated Oil Reservoirs

The pressure in these reservoirs falls at two on the pressure-temperature envelope. Saturated oil reservoirs have equal fluid bubble points and initial reservoir pressures. The saturation shows that the fluid in this reservoir cannot take extra gas bubbles unless the pressure is increased.

Gas-Cap Reservoirs

Gas-cap reservoirs are also called two-phase reservoirs. In these reservoirs, the bubble point pressure of the fluid is higher than the initial reservoir pressure. In other words, two-phase reservoirs are saturated with gas and contain gases in the reservoir trap’s upper portions.

Knowing that you are drilling an oil reservoir is not enough. Understanding the oil reservoir you are working with ensures that you get efficient production from the reservoir. With this knowledge, you can engineer your flow-rate based on the type of reservoir you are dealing with.